sunshinecorp: All Lucasfilm/Lucasarts adventure games really. Every single one of them, can't just pick one.
Yes, you can:
The Secret of Monkey Island.
RWarehall: I'd start with Sam & Max Hit the Road and the Monkey Island games to complement what is already on GoG.
I'd start with
The Secret of Monkey Island too, yes, excellent choice.
I guess if they actually bring that to GOG, I might finally get that remake version, which I have been semi-boycotting* so far.
* boycott = not buying, cause there's no DRM-free version; semiboycott = I'm not sure if I even want that remake, as the original was perfect, but might want to complete my MI collection
But as I have all LucasArts adventures already, most of them in several copies, personally I'm waiting more of their Star Wars titles.
And as the original question was not specifically about LucasArts, but about Disney too, I wouldn't mind seeing the old DuckTales game here too. I don't know/remember the developer/publisher, but most likely it needs an approval from Disney to enter any game stores.